1. Technical Field of the Invention
The invention relates in general to a data encoding and decoding apparatus and the corresponding data processing method thereof for processing multi-channel audio signal. The MPEG-2 international video and audio standard has adopted the AC-3 high-fidelity multi-channel audio signal compression technique developed by the DOLBY Inc., in which the subband coding analysis and synthesis filters utilize time-domain aliasing cancellation technique. The invention provides a highly-efficient and compact technique for implementing the encoding and decoding process of the time-domain aliasing cancellation apparatus.
2. Background Art of the Invention
Due to increased demands for high-quality audio and video entertainment for private uses, multi-channel high-fidelity audio equipments are gradually moving from the public entertainment facilities, like the movie theaters, into the living room for many families. To achieve wide-spread private uses, the cost of these equipments must be lowered substantially. The compression apparatus of these multi-channel high-fidelity audio equipments is the key element of the cost reduction efforts. Manufacturing cost of these equipments can be significantly reduced simply by developing simple and highly efficient signal processing technique to be implemented in semiconductor devices.
Currently, the most widely adopted high-end audio signal compression technique is the AC-3 multi-channel high-fidelity audio signal compression technique invented by DOLBY Inc. Because its subband encoding filter using the time-domain aliasing cancellation (TDAC) technique requires a large amount of computations, the TDAC apparatus becomes the key technology for audio compression. The TDAC analysis and synthesis filters are also treated as the modified discrete cosine transform and the inverse modified discrete cosine transform. Dolby Inc. employs Fast Fourier Transform (FFT) to achieve the TDAC operation. The details of this technique can be found in the documentation Dolby AC-3, Multi-Channel Digital Audio Compression System Algorithm Description, Dolby Laboratories Information, Feb. 22, 1994 Revision 1.12, Dolby Laboratories Inc. Also, according to Duhamel's suggestion (P. Duhamel, "Implementation of `Split-Radix` FFT Algorithm for Complex, Real, and Real-Symmetric Data," IEEE Trans. on Acoustics, Speech and Signal Processing, Vol. ASSP-34, No. 2, pp. 285-295, April 1986), the FFT can be substituted by split-radix FFT (SRFFT) to speed up the compression and de-compression operations. Nevertheless, the SRFFT still requires tremendous amount of computations. Thus, any manufacturer possessing a simple and fast technique for TDAC will have an advantage the highly competitive international market.